There has been known an oil pressure control system for an automatic transmission, which supplies hydraulic oil to an automatic transmission for automatically shifting gears of a vehicle by engaging or releasing a plurality of clutches and brakes in accordance with a shift range selected by a driver of the vehicle. The oil pressure control system for the automatic transmission includes: a manual valve having a sleeve with a plurality of openings connected to the clutches and the brakes, and a spool reciprocally inserted in the sleeve; a detent lever; an engagement member; a motor; and the like. In the oil pressure control system for the automatic transmission, an oil passage for hydraulic oil to be supplied to the clutch and the brake is changed by positioning of the spool with respect to the sleeve. The positioning of the spool with respect to the sleeve is performed by engaging the engagement member, which is coupled to the spool, with any of a plurality of engagement grooves in the detent lever. That is, a quantity and pressure of the hydraulic oil to be supplied to the clutch and the brake are decided in accordance with the engagement position between the detent lever and the engagement member. A motor capable of rotating the detent lever is provided in the oil pressure control system for the automatic transmission. The motor adjusts the engagement position between the detent lever and the engagement member. For example, Patent Literature 1 describes a controller of an oil pressure control system for an automatic transmission in which, when a shift range is switched, a detent lever is rotated within a predetermined stop range based on a count value of a pulse signal of an encoder for detecting a rotation angle of a motor, and thereafter, the motor is driven in minute steps until the count value becomes a target count value.
Patent Literature 1: JP-2014-101919-A (corresponding to US 2014/0139171 A1)